Wavelength conversion structure, manufacturing methods thereof, and lighting emitting device including the wavelength conversion structure

ABSTRACT

A wavelength conversion structure comprises a phosphor layer comprising a first part and a second part formed on the first part, wherein the first part and the second part have a plurality of pores, a first material layer formed in the plurality of pores of the first part, a second material layer formed in the plurality of pores of the second part and a plurality of phosphor particles, wherein the plurality of phosphor particles is distributed in the first material layer and the second material layer.

TECHNICAL FIELD

The application is related to a wavelength conversion structure and themanufacturing method thereof and particularly to a wavelength conversionstructure and the manufacturing method thereof with high lightextraction efficiency.

REFERENCE TO RELATED APPLICATION

This application claims the right of priority based on TW applicationSerial No. 100128104, filed on Aug. 5, 2011, and the content of which ishereby incorporated by reference in its entirety.

DESCRIPTION OF BACKGROUND ART

In recent years, because people have paid more attention to the energyproblem, many new lighting tools with low energy consumption have beendeveloped to save the energy. Therefore, the light emitting diode (LED)which has many advantages, such as high lighting efficiency, low powerconsumption, non-mercury and long lifetime, becomes the promisinglighting tool of next generation.

The white LED used for lighting is produced by the blue LED chip andphosphor. The white light emitted from the white LED can be formed byusing the blue light, which is emitted from the blue LED chip, to excitethe yellow phosphor, for example, YAG (Yttrium Aluminum Garnet,Y₃Al₅O₁₂), to emit the yellow light, and then mixing the two lights.

The phosphor coating methods comprise conformal coating method andremote phosphor coating method. The conformal coating method coats thephosphor on the surface of the LED chip to form the phosphor layer.Because the phosphor is directly coated on the LED chip, the phosphorlayer has a uniform thickness. But, the light emitted from the phosphorlayer may be absorbed by the LED chip and the carrier so the totallighting efficiency of the LED chip may be decreased. On the other hand,when the LED chip emits light, the temperature of the LED chip is around100° C. to 150° C., and due to the direct contact of the LED chip andthe phosphor layer, the heat produced by the LED chip may deterioratethe phosphor layer and decrease the transformation efficiency of thephosphor layer.

The remote phosphor method can solve the above mentioned problems of theconformal coating method. The remote phosphor method separates thephosphor layer and the LED chip to prevent the light emitted by the LEDchip directly absorbed by the phosphor layer. And, due to the separationof the phosphor layer and the LED chip, the phosphor layer is not easyto be deteriorated by the heat produced by the LED chip.

When the particles of the phosphor layer absorb the light emitted by theLED chip, the particles are excited and emit the light with anothercolor. However, the light emitted by the particles is omni-directional,including the light emitted toward the LED chip. Since the refractiveindex of the encapsulation resin is different from that of the phosphorlayer, the total reflection of the light emitted by the particles happeneasily so the light efficiency is decreased.

SUMMARY OF THE DISCLOSURE

A wavelength conversion structure comprises a phosphor layer comprisinga first part and a second part formed on the first part, wherein thefirst part and the second part have a plurality of pores, a firstmaterial layer formed in the plurality of pores of the first part, asecond material layer formed in the plurality of pores of the secondpart and a plurality of phosphor particles, wherein the plurality ofphosphor particles is distributed in the first material layer and thesecond material layer.

A method of manufacturing a wavelength conversion structure comprisesthe steps providing a substrate, forming a phosphor layer on thesubstrate, the phosphor layer comprising a first part and a second part,wherein the first part and the second part comprise a plurality ofpores, forming a first material layer in the plurality of pores of thefirst part and forming a second material layer in the plurality of poresof the second part.

A light-emitting device, comprises a substrate, a light-emitting unitdisposed on the substrate, a first light guide layer covering thelight-emitting unit on the substrate and a wavelength conversionstructure on the first light guide layer, wherein the wavelengthconversion structure comprises, a phosphor layer comprising a first partand a second part, wherein the first part on the first light guidelayer, the second part on the first part, and the first part and thesecond part have a plurality of pores, a first material layer formed inthe plurality of pores of the first part and a second material layerformed in the plurality of pores of the second part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the wavelength conversion structure in accordance with oneembodiment of the present application;

FIG. 2 shows the first part of the wavelength conversion structure withthe first material layer disposed thereon;

FIG. 3 shows the upper surface of the second material layer of thesecond part higher than the top surface of the phosphor layer;

FIG. 4 shows the scanning electron microscope (SEM) diagram of thephosphor layer of the wavelength conversion structure;

FIG. 5 shows the scanning electron microscope (SEM) diagram of thephosphor layer on the first material layer;

FIG. 6 shows the scanning electron microscope (SEM) diagram of thesecond material layer on the first material layer;

FIG. 7 shows the light emitting device in accordance with one embodimentof the present application.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary embodiments of the present application will be described indetail with reference to the accompanying drawings hereafter. Thefollowing embodiments are given by way of illustration to help thoseskilled in the art fully understand the spirit of the presentapplication. Hence, it should be noted that the present application isnot limited to the embodiments herein and can be realized by variousforms. Further, the drawings are not precise scale and components may beexaggerated in view of width, height, length, etc. Herein, the similaror identical reference numerals will denote the similar or identicalcomponents throughout the drawings.

Specially, it needs to be described that when a component or a materiallayer is described to be disposed on or connected to another one, thecomponent or the material layer may be directly disposed on or connectedto another one, or may be indirectly disposed on or connected to anotherone, that means there is another component or material layer betweenthereof. On the contrary, when a component or a material layer isdescribed to be directly disposed on or directly connected to anotherone, there is no any other component or material layer between thereof.

FIG. 1 shows the wavelength conversion structure according to oneembodiment of the application. A wavelength conversion structure 10comprises a conductive substrate 101, a phosphor layer 102, a firstmaterial layer 103, and a second material layer 104. The phosphor layer102 on the conductive substrate 101 comprises phosphor particles,wherein multiples pores are between the phosphor particles. The phosphorlayer 102 comprises a first part 105 and a second part 106, wherein thefirst part 105 is on the conductive substrate 101, the second part 106is on the first part 105, and the sum of the thickness of the first part105 and the second part 106 is equal to the thickness of the phosphorlayer 102. The first material layer 103 is on the conductive substrate101, and the first material layer 103 is formed by filling the pores ofthe first part 105 with inorganic compound to form a thin film, whereinthe thickness of the thin film is smaller than the phosphor layer 102.The second material layer 104 on the first material layer 103 is formedby filling the pores of the second part 106 with glue.

The conductive substrate 101 is transparent and electrically conductiveand the material the conductive substrate 101 can be, but not limited totransparent conductive inorganic compound (TCO). The phosphor layer 102is formed on the conductive substrate 101, wherein the material of thephosphor layer 102 can include but not limited to yellow ceramicphosphor. The diameter of the phosphor particles of the phosphor layer102 is in a range of 225 nm ˜825 nm, and there are pores between thephosphor particles. The phosphor layer 102 comprises the first part 105and the second part 106, wherein the thickness of the first part 105 issmaller than the thickness of the phosphor layer 102, and the ratio ofthe thickness of the first part 105 to the thickness of the phosphorlayer 102 is in a range of 0.5˜0.9. The thickness of the second part 106is equal to the difference of the thickness between the phosphor layer102 and the first part 105.

FIG. 2 shows the inorganic compound is filled in the pores of the firstpart 105 between the phosphor particles to form the first material layer103. The material of inorganic compound can include but not limited toZnO, Al₂O₃, ITO, AZO or InGaZnO (IGZO). Take the phosphor layer 102 ofyellow ceramic phosphor for example, the refractive index of the yellowceramic phosphor is about 2, the material of inorganic compound ispreferably selected from the material, of which the refractive index isnear 2, such as ZnO of which the refractive index is about 1.8 to 2. Itmay reduce the loss of the lighting efficiency due to the difference ofthe refractive index between the different materials because therefractive indices of the first material layer 103 and the phosphorlayer 102 are similar. The inorganic compound which is filled in thepores between the phosphor particles is also used for binding thephosphor particles to increase the mechanical strength of the phosphorlayer 102.

The glue is filled in the pores of the second part 106 to form thesecond material layer 104 in the wavelength conversion structure 10 asshown in FIG. 1. The material of the second material layer 104 caninclude but not limited to silicon, of which the refractive index isabout 1.45. In another embodiment, the material of the second materiallayer 104 comprises other material such as glass (refractive index is1.51.9), resin (refractive index is 1.5˜1.6), TiO₂ (refractive index is2.2˜2.4), SiO₂ (refractive index is 1.5˜1.7) or MgF (refractive index isabout 1.38). The material of the second material layer 104 can alsoinclude inorganic and organic material, of which the refractive index isabout between 1.3 and 1.6.

The thickness of the second part 106 is equal to the difference of thethicknesses between the phosphor layer 102 and the first part 105. Inanother embodiment, the thickness of the second material layer 104 islarger than the thickness of the second part 106, and the upper surface124 of the second material layer 104 is higher than the top surface 126of the phosphor layer 102, which results in a smoother surface of thewavelength conversion structure 10 as FIG. 3 shows.

Thereinafter, the manufacturing method of the wavelength conversionstructure 10 is introduced according to the embodiment. First, theconductive substrate 101 is disposed into an electrophoresis apparatus,wherein the conductive substrate 101 can be ITO glass. The phosphorparticles are deposited on the surface of the ITO glass byelectrophoresis technology to form a phosphor layer 102, and thescanning electron microscope (SEM) picture is shown in FIG. 4. Thephosphor layer 102 comprises a material such as phosphor to convert thelight of the first wavelength into the light of the second wavelength.The technology to deposit the phosphor layer 102 is not limited to theelectrophoresis technology, and also comprises gravity deposition. Next,the transparent inorganic compound such as ZnO is deposited into thepores of the first part 105 of the phosphor layer 102 by electroplatingto form the first material layer 103. By filling the pores of the firstpart 105 with the transparent oxide, of which the refractive index iscloser to the phosphor, it reduces the loss from light scattering andincreases the light extracting efficiency. The inorganic compound may beused for binding the phosphor particles to enhance the mechanicalstrength of the phosphor layer 102, which is shown in the scanningelectron microscope (SEM) diagram of FIG. 5. During the depositionprocess, the thickness of the first material layer 103 is adjustablebased on the sizes of the phosphor particles and/or the pores. Themethod of depositing the first material layer 103 is not limited toelectroplating and also comprises other methods that can fill theinorganic compound into the pores of the first part 105, such aschemical vapor deposition (CVD) and sol-gel. Finally, the second part106 of the phosphor layer 102 is filled with glue, which is shown in thescanning electron microscope (SEM) diagram of FIG. 6. The detail stepsof filling with glue are well known by the person skilled in the art,and these are not described here again. The thickness of the wavelengthconversion structure 10 can be uniform or non-uniform.

The diagram of the light emitting device according to another embodimentis shown in FIG. 7. The light emitting device 20 comprises a packagingsubstrate 111, a light emitting diode 110, a lead frame 112, a lightguide layer 113, and a wavelength conversion structure 10. The lightemitting diode 110 is located on the packaging substrate 111. The lightguide layer 113 covers the packaging substrate 111 and the lightemitting diode 110. The light emitting device 20 includes theabove-mentioned wavelength conversion structure 10, wherein thewavelength conversion structure 10 and the light emitting diode 110 areseparated by the lead frame 112, and the phosphor does not directlycontact the light emitting diode 110, which prevents the light emittedfrom the phosphor layer 102 directly absorbed by the light emittingdiode 110. Also, because the phosphor is separated from the lightemitting diode 110, the heat from the light emitting diode 110 dose noteasily influence the phosphor and the phosphor of the phosphor layer 102does not deteriorate easily.

The light guide layer 113 in the embodiment is a light passing layer,which can be a material layer to improve the light extractionefficiency. In this embodiment, the light guide layer 113 has multiplematerial layers with gradient refractive index (GRIN). In thisembodiment, the multiple material layers of the light guide layer 113can include but not limited to Si₃N₄ (refractive index is 1.95), Al₂O₃(refractive index is 1.7), and silicone (refractive index is 1.45). Inanother embodiment, the multiple material layers of the light guidelayer 113 can also include the combination of other materials. Becausethe difference of the refractive indices between the adjacent layers ofthe multiple material layers of the light guide layer 113 is small andthe refractive index is smaller as the layer of the multiple materiallayers of the light guide layer 113 away from the light emitting diode110, the light guide layer 113 is able to reduce the total reflection.The multiple material layers of the light guide layer 113 can includebut not limited to the combination of glass (refractive index is1.5˜1.9), resin (refractive index is 1.5˜1.6), diamond like carbon (DLC,refractive index is 2.02.4), titanium (TiO₂, refractive index is2.2˜2.4), silicon oxide (SiO₂, refractive index is 1.5˜1.7), ormagnesium fluoride (MgF, refractive index is 1.38). In this embodiment,the light emitting diode 110 can be GaN blue light LED chip, of whichthe refractive index is 2.4. Therefore, by using the small difference ofthe refractive indices between the adjacent layers and the gradientrefractive index, it is able to reduce the total reflection of the lightemitted from the light emitting diode 110.

In the light emitting device 20, the wavelength conversion structure 10is disposed on the light guide layer 113. The light emitted from thelight emitting diode 110 passes through the light guide layer 113 andenters the wavelength conversion structure 10. After passing through thelight guide layer 113 having the multiple material layers and enteringthe second material layer 104 with smaller refractive index than thelight guide layer 113, the light enters the phosphor layer 102 and thefirst material layer 103, wherein the refractive indices thereof aresimilar. Since the difference of refractive indices between the adjacentlayers is small, it is able to prevent the light loss due to the totalreflection. And, since the refractive indices of the inorganic compoundand phosphor particles are similar, it is also able to reduce thescattering between the phosphor particles. In this embodiment, the lightemitting device 20 is a flat encapsulating structure. In otherembodiments, the conductive substrate 101 of the wavelength conversionstructure 10 is not limited to be a flat panel, and also can be aconvex, a concave or a triangle cones. In other words, the surface ofthe conductive substrate 101 can be a flat surface, a curved surface, ora convex surface.

Table 1 shows the comparison of the testing light extraction efficiencyof the light emitting device 20 with the wavelength conversion structure10, wherein the light extraction efficiencies of the pores of thephosphor layer 102 filled with only silicone and filled with inorganiccompound (ITO), ZnO and silicone are compared. According to Table 1, thelight extraction efficiency of the light emitting device 20 is 32.15Lumen/Watt, as the pores of the phosphor layer 102 are filled with onlysilicone; the light extraction efficiency of the light emitting device20 is in a range 35.9˜36.8 Lumen/Watt, as the pores of the phosphorlayer 102 are filled with ITO, ZnO and silicone, wherein the lightextraction efficiency of the light emitting device 20 is 35.9, as theZnO plating duration is 45 min, and the light extraction efficiency ofthe light emitting device 20 is 36.8, as the ZnO plating duration is 90min. In this embodiment, the light extraction efficiency of thewavelength conversion structure 10 comprising inorganic compound mixedwith silicone is 14% higher than that of the wavelength conversionstructure 10 without inorganic compound. The light extraction efficiencyof the wavelength conversion structure 10 comprising ZnO of which theplating duration is 90 min is higher than that of the wavelengthconversion structure 10 comprising ZnO of which the plating duration is45 min.

TABLE 1 The light extraction efficiency vs. the composition of thewavelength conversion structure 10 Light extraction Comparison of theefficiency Light extraction [Lumen/Watt] efficiency (%) Silicone,without ITO and ZnO 32.1521 Reference Plating ZnO 90 min + silicone36.80457 14.47 with ITO Plating ZnO 45 min + silicone 35.909533 11.69with ITO

The foregoing description of preferred and other embodiments in thepresent disclosure is not intended to limit or restrict the scope orapplicability of the inventive concepts conceived by the Applicant. Inexchange for disclosing the inventive concepts contained herein, theApplicant desires all patent rights afforded by the appended claims.Therefore, it is intended that the appended claims include allmodifications and alterations to the full extent that they come withinthe scope of the following claims or the equivalents thereof.

1. A wavelength conversion structure, comprising: a phosphor layercomprising a first part and a second part formed on the first part,wherein the first part and the second part have a plurality of pores; afirst material layer formed in the plurality of pores of the first part;a second material layer formed in the plurality of pores of the secondpart; and a plurality of phosphor particles, wherein the plurality ofphosphor particles is distributed in the first material layer and thesecond material layer.
 2. A wavelength conversion structure according toclaim 1, further comprises a substrate on a side of the first materiallayer.
 3. A wavelength conversion structure according to claim 2,wherein the substrate comprises a conductive substrate.
 4. A wavelengthconversion structure according to claim 1, wherein the first materiallayer comprises a metallic oxide, and/or the second material layercomprises silica or glass.
 5. A wavelength conversion structureaccording to claim 1, wherein the refractive index of the first materiallayer is between 1.8 and 2, and/or the refractive index of the secondmaterial layer is between 1.3 and 1.6.
 6. A wavelength conversionstructure according to claim 1, wherein the phosphor layer comprisesyellow phosphor.
 7. A wavelength conversion structure according to claim1, wherein a thickness of the first part is 0.5 to 0.9 times a thicknessof the phosphor layer.
 8. A wavelength conversion structure according toclaim 1, wherein an upper surface of the second material layer is higherthan a top surface of the phosphor layer.
 9. A wavelength conversionstructure according to claim 2, wherein a surface of the substrate is aflat surface, a curved surface, or a convex surface.
 10. A wavelengthconversion structure according to claim 1, wherein the difference ofrefractive index between the phosphor layer and the first material layeris smaller than 0.3.
 11. A wavelength conversion structure according toclaim 2, wherein the refractive index of the substrate is smaller thanthat of the phosphor layer.
 12. A method of manufacturing a wavelengthconversion structure comprising the steps: providing a substrate;forming a phosphor layer on the substrate, the phosphor layer comprisinga first part and a second part, wherein the first part and the secondpart comprise a plurality of pores; forming a first material layer inthe plurality of pores of the first part; and forming a second materiallayer in the plurality of pores of the second part.
 13. A method ofmanufacturing a wavelength conversion structure according to claim 12,wherein the phosphor layer is formed on the substrate by electrophoresisor gravity deposition method.
 14. A method of manufacturing a wavelengthconversion structure according to claim 12, wherein the first materiallayer is formed in the plurality of pores of the first part byelectroplating method, chemical vapor deposition method, or sol-gelmethod, and/or the second material layer is formed by filling with glue.15. A method of manufacturing a wavelength conversion structureaccording to claim 12, wherein a thickness of the first part is 0.5 to0.9 times a thickness of the phosphor layer.
 16. A method ofmanufacturing a wavelength conversion structure according to claim 12,wherein an upper surface of the second material layer is higher than atop surface of the phosphor layer.
 17. A method of manufacturing awavelength conversion structure according to claim 12, wherein therefractive index of the substrate is smaller than that of the phosphorlayer.
 18. A method of manufacturing a wavelength conversion structureaccording to claim 12, wherein a thickness of the wavelength conversionstructure is uniform or non-uniform.
 19. A method of manufacturing awavelength conversion structure according to claim 12, wherein thedifference of refractive index between the phosphor layer and the firstmaterial layer is smaller than 0.3.
 20. A light-emitting device,comprising: a substrate; a light-emitting unit disposed on thesubstrate; a first light guide layer covering the light-emitting unit onthe substrate; and a wavelength conversion structure on the first lightguide layer, wherein the wavelength conversion structure comprises: aphosphor layer comprising a first part and a second part, wherein thefirst part on the first light guide layer, the second part on the firstpart, and the first part and the second part have a plurality of pores;a first material layer formed in the plurality of pores of the firstpart; and a second material layer formed in the plurality of pores ofthe second part.